Nutrient State-Dependent Ascarosides and Nematode Immune Response Limit the Predation of Arthrobotrys oligospora.

Nematode-trapping fungi act as predators of nematodes in soil ecosystems, forming a typical predator-prey relationship. However, this interaction is frequently influenced by environmental factors such as nutrient state. In this study, we demonstrate that starved nematodes had better chances of escaping A. oligospora predation by inhibiting A. oligospora trap formation. Starved nematodes showed downregulated acyl-CoA oxidase genes (acox-1.2/1.3/1.4) and reduced ascaroside pheromone production (ascr#1/#3/#5/#9), thus diminishing A. oligospora trap induction. In soils with uneven nutrient content, nutrient deficiencies can activate this mechanism locally, thereby reducing predation. When avoidance fails, nematodes rely on canonical innate immune pathways (FSHR-1, ATFS-1, and PMK-1) to improve survival during capture. In response to this predation, nematodes have evolved multiple strategies to defend against these pressures, closely linked to their nutritional status. Together, these findings link local nutrient availability to both fungal predation efficiency and the robustness of nematode defenses in soil ecosystems.